1. Field of the Invention
The present invention relates to a gas turbine blade having a shower head cooling mechanism.
2. Description of the Prior Art
In an air cooled blade of a high temperature gas turbine, film cooling has now become established as an indispensable art. With reference to FIGS. 3 and 4, a conventional type of cooling is illustrated. FIG. 3 is a cross sectional view of the an air cooled blade, and FIG. 4 is a perspective view showing an arrangement of shower head cooling holes in a blade leading edge portion.
Generally in a high temperature gas turbine blade, as shown in FIG. 3, shower head cooling holes SC are provided in a blade leading edge portion. Film cooling holes FC are provided on an upstream side of the a blade dorsal portion and on a downstream side of a blade ventral portion and pin fin holes PC are provided in a blade trailing edge portion.
The shower head cooling holes SC, as shown in FIG. 4, are bored in a leading edge portion of a blade 2 so as to be arranged in a straight line toward a blade hub side HS from a blade tip side TS. Air is blown from the cooling holes in an opposite direction relative to the gas flow.
Shower cooling and film cooling relate to an art that enhances cooling efficiency by covering a blade surface with a cooling air that is blown over a gas flow surface.
If the cooling air is blown too strongly, however, the cooling air causes a peeling from the blade surface so as to mix with a main flow of the gas which results in a reduced effect of the film cooling, or if the cooling air is blown too weakly, it will not provide a proper cooling effect due to a shortage of the cooling air amount. Accordingly, these considerations must be taken into account so that the blade surface will be covered by an optimal film of air.